The present invention generally relates to output selection and, more particularly, to a system and method for selectively connecting one of at least two outputs of an associated circuit to an output node, such as to provide a selectable switch mode.
Various types of proximity sensors are used for detecting the presence or absence of an object relative to a monitored zone. Common types of non-contact proximity sensors include inductive proximity sensors, capacitive proximity sensors, ultrasonic proximity sensors, and photoelectric sensors. Such sensors, for example, may be used in motion or position applications, conveyor system control applications, process control applications, robotic welding applications, machine control applications, liquid level detection applications, as well as other applications.
One type of proximity sensor circuit employs a non-contact, solid state electronic switch that turns ON and OFF in response to detecting the presence or absence of a target within a monitored zone. By way of example, the sensor is an inductive proximity sensor that includes an oscillator for providing an oscillating signal to an inductive coil, which provides an electromagnetic field. As an electrically conductive target moves within the field, eddy currents develop within the target in response to the oscillating electromagnetic field. The eddy currents alter the amplitude of the oscillating signal being provided to the coil. The amplitude of the oscillator signal typically is evaluated to provide an output signal indicative of the presence or absence of the object within the electromagnetic field. The sensor provides an output signal based on the sensed amplitude of the oscillating signal.
The output signal may be utilized to control part of a process or a machine based on the sensed presence (or absence) of a target within a zone monitored by the sensor. For example, an associated motor may be activated when the sensor signal indicates the presence of a target within the monitored zone and deactivated when no target is within the zone. Some implementations, however, may require a different operating mode based on the sensor signal. For example, it may be desirable to deactivate a motor when a target is sensed to be within the monitored zone and activate it when no target is within the zone.
In order to accommodate both types of switch operating modes, two types of electronic switching devices are used in connection with proximity sensors, namely, normally open and normally closed switching devices. In order to help minimize inventory requirements, some electric switching devices (integrated circuits) include two complementary outputs; one output corresponding to a normally open operating mode and the other a normally closed operating mode. While the dual operating mode circuit reduces inventory requirements, the individual installing the system must properly connect the switch so as to provide the desired type of output signal.
Switch circuits have been proposed that operate in a normally-open or normal closed operating according to the circuit""s connection to a supply voltage. U.S. Pat. No. 5,229,653, for example, discloses a connection programmable electronic switching device that operates in a different mode depending on the polarity at which the device is connected to an external power supply. The ""653 patent discloses a two-wire input circuit in which power inputs serve a dual function, acting as both a power source for the switching circuit and as an output for the circuit. The switching circuit includes two electronic switches. Each switch is controlled to carry current from an associated complementary output only in one direction to a power input depending on the polarity of the power inputs.
The present invention relates to a system and method for selectively connecting one of at least two outputs of an associated circuit to an output node based on the relative voltage between a pair of power supply inputs. The system includes a first pair of switches, each of which is coupled to a respective one of the power supply inputs so as to operate in a mutually exclusive manner based on the relative voltage potential between the inputs. That is, when the system is connected to a power source in a first manner, one switch of the first pair of switches is ON (or closed) and the second switch is OFF (or open). When the system is connected to the power source in another manner, the one switch is OFF (or open) and the other switch is ON (or closed). Each switch of the first pair of switches is coupled to a control input of a second pair of switches, each of which is coupled to a different corresponding output of an electronic switch control circuit, such as a proximity sensor circuit. Each switch of the second pair of switches is activated in response to activation of its associated switch of the first pair of switches. When a first switch of the second pair of switches is activated, one of the outputs is coupled to an output node. When a second switch of the second pair of switches is activated, the other output is coupled to the output node.
The outputs of the control circuit, for example, are complementary outputs, in which each output corresponds to a different operating mode of the control circuit. For example, one output may provide a control signal for a normally-open operating configuration and the other provide a control signal for a normallyclosed operating configuration. Therefore, depending on the connection of the inputs to a power supply, the electronic switch may be connected to the power supply so as to operate either in a normally open configuration or a normally closed configuration, with a corresponding output signal being provided to the output node. By way of example, the output node may be employed to control an actuatable component or device based on the operating condition of the control circuit. As a result, end users (e.g., customers) that require both normally-open and normally closed switch configurations need only stock a single type of switch circuit, in accordance with an aspect of the present invention.
Another aspect of the present invention provides a system for selectively connecting one of at least two outputs of an associated circuit to an output node. The system includes a pair of inputs for receiving different relative voltage levels. A first switch is operatively coupled to a first of the inputs and a second switch operatively coupled to a second of the inputs. Each of the first and second switches operates mutually exclusively according to the voltage potential between the pair of inputs. A third switch is operatively coupled between a first output of the associated circuit and the first switch. When the third switch is activated in response to activation of the first switch, it couples the first output to the output node. The system further includes a fourth switch operatively coupled between a second output of the associated circuit and the second switch. When the fourth switch is activated in response to activation of the second switch, it couples the second output to the output node.
Yet another aspect of the present invention provides a system for selecting an operating mode of a proximity sensing circuit. The system includes input means for coupling to a source of electrical energy to apply a voltage potential across the input means. A first pair of switch means is operatively coupled to the inputs means. When each switch means of the first pair of switch means is activated, it activates a corresponding one of a second pair of switch means based on the voltage potential across the pair of input means. One of the second pair of switch means and one of the first pair of switch means are operative to connect one output of at least two outputs of the proximity sensing circuit to an output node based on the relative voltage across the input means. Another of the second pair of switch means and another of the first pair of switch means are operative to connect another output of the at least two outputs of the proximity sensing circuit to the output node based on the relative voltage across the input means.
Still another aspect of the present invention provides a method for selectively connecting one of at least two outputs of an associated circuit to an output node based on a relative voltage potential between a pair of inputs. The method includes electrically coupling the pair of inputs to a source of electrical energy to apply a relative voltage potential across the pair of inputs. One switch of a first pair of switches is selectively activated based on the voltage potential across the pair of inputs. One switch of a second pair of switches is activated in response to the activated one of the first pair of switches. One output of the at least two outputs is connected to the output node based on which one of the second pair of switches is activated.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.